Refrigeration control system



/ Patented-Sept. 5, 1944 UNITED STATES PATENT OFFICE 2,357,758 Y I anraronaxrron couraor. SYSTEM Alwin 13; Newton, Minneapolis, Minn, assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn, a corporation of Delaware Application April 2'1, '1940, Serial No. 332,001

3 Claims. I (01. 62-8) This invention relates to a control'system for a refrigerating apparatus having evaporator means and a valve responsive to the outlet temperature of the refrigerant for regulating the flow of refrigerant to the evaporator means to maintain a desired amount of liquid refrigerant in the evaporator means.

Anobject of this invention is to provide a novel and commercially practicable arrangement for regulating the amount of liquid refrigerant in an evaporator and to prevent reducing this amount ,of refrigerant below a predetermined minimum.

These objects are accomplished by producing a false temperature at the temperature sensitive element of .the usual thermostatic expansion valve by introducing refrigerant towards or at the end of the evaporator or evaporators. This refrigerant upon evaporating creates a. lower temperature at the sensitive element of the thermostatic expansion valve thereby acting to change the control point thereof. By taking this refrigerant from the downstream side of the expansion valve i so that-it has already been partially expanded,

reasonable quantities thereof can be utilized.

Also, by introducing this refrigerant at a distance from the sensitive element of the thermostatic expansion valve its effect is reduced whereby the quantity utilized may be further increased. This also prevents any liquid refrigerant from reaching the sensitive element. As a result, the quantity of refrigerant introduced is made large enough to enable its control by an ordinary valve which can be commercially produced in quantities ,by' regular production methods.

Also, by introducing this refrigerant at a point frigerant intothe evaporator in accordance with the condition of the medium being controlled by the evaporator means. For example, it may be controlled by the temperature or relative humidity of thespace being controlled.

i A further object of this invention is to apply the arrangement outlined above to a refrigerating apparatus having a plurality of evaporators arranged in parallel, a distributor for distributing liquid refrigerant to the evaporators and a common outlet for the evaporators. v

Other objects and advantages will become apparent to those skilled in the art upon reference to the accompanying specification, claims and drawing, in which is diagrammatically illustrated the preferred form of this invention.

Referring now to the drawing, an air conditionirzg chamber is designed at l0. Located in the chamber I0 is a cooling means II in the form of an evaporator unit. The cooling means is divided into three parallelly arrangedv evaporators l2, l3, and I4 having a common outlet IS. A distributor I6 of conventional design. distributes liquid refrigerant to the parallelly arranged evaporators l2, I3, and I4. Outside or return air or a combination thereof may be passed through the air conditioning chamber l0 and over the evaporator unit II to the space being controlled,

all as is well known in the art. Refrigerant is circulated through the evaporators l2, I3, and I4 by means of .a refrigeratingf apparatus generally designated at 23. The refrigerating apparatus may comprise a compressor 24 operated by an electric motor '25.. Compressed refrigerant is discharged from the compressor 24 through a high'pressure line 26 into a condenser 21. 'Condensed refrigerant is collected in a receiveri28 and flows through a liquid line 29 to the distributor I6 under the control of an expansion valve 30 and 'a normally open valve II. Evaporated refrigerant is withdrawn from.- the evaporators I2, 13, and i4 through the common outlet l5 and a suction line 3| by the compressor 24.

Poweris supplied to the compressor motor 25 by means of line wires 33 and 34 leading from some source of power, not shown, and the'operation of the compressor motor 25 and hence the compressor 24 is controlled by'a combined suction pressure and head pressure responsive controller 35 which may be of the typeshown and described in application Serial No. 196,447 filed by Albert L. Judson and Carl GrKronmiller on controller 35, wire 38 and compressor motor 25.

back to the other line wire. to place. the compressor 24 in operation. compressor 24 remains in operation until either the suction pressure decreases to a predetermined low value or the head pressure increases to a predetermined high value at which time the motor circuit is broken to stop operation of the compressor. Accordingly the compressor motor and hence the compressor 24 are operated to'maintain the suction pressure within predetermined limits. In case the head pressure should become excessive operation of the compressor 24 is stopped.

The expansion valve which regulates the flow of liquid refrigerant to the distributor, I 5 is of the conventional thermostatic type having a diaphragm chamber 48. One side of the diaphragm located in the diaphragm chamber 40 is connected by a pipe M to the common outlet I5 of the evaporators I2, I3 and I4 so that the expansion valve is operated in accordance with pressure conditions existing within the evaporators I2, I3 and I 4. The other side of the diaphragm is connected through a capillary tube 42 to a bulb 43 charged with a volatile fluid and located on the suction line 3| so as to respond to the temperature of the superheated refrigerant as it leaves the evaporators I2, I3 and I4. Upon an increase in pres- A pipe 45 connected between the expansion 1 valve 30 and the valve I1 is utilized for supplying auxiliary liquid refrigerant to the evaporators I2, I3, and I4 for the purpose of artificially cooling the bulb 43 of the thermostatic expansion valve to change the amount of liquid refrigerant maintained in the evaporators I2, I3 and I4. This pipe 45 leads into a distributor 41 and the supply of this auxiliary liquid refrigerant to the distributor 41 is regulated by a valve 45. Pipes 48, 49 and 50 extend between the distributor 4I and-the evaporators I 2, I3 and I4, respectively. The pipes 48, 49 and 50 are shown connected into the evaporators I2, I3 and I4 at a point between the inlets and outlets of'these evaporators.

When the valve 45 is opened, liquid refrigerant is supplied adjacent the 'outletof the evaporators I2, I3 and I4 and this liquid refrigerant expands in the evaporators and thereby cools the superheated refrigerant flowing past the bulb 43 of the thermostatic expansion valve. When the bulb 43 of the thermostatic expansion valve is thus decreased in temperature the thermostatic expansion valve 38 is moved towards a closed position to decrease the supply of refrigerant to the evaporators I2, I3 and n. Thus the amount of liquid refrigerant maintained in the evaporators I2, I3'and I4 is decreased, the amount of decrease varying with the amount of liquid refrigerant admitted to the evaporators I 2, I3 and I4 by the valve 45. By graduatingly positioning the valve 45 the amount of liquid refrigerant maintained in the evaporators I2, I3'and I4 may therefore be graduatingly varied.

The valve 45 may be manually positioned or it may be positioned in accordance with the condition of the medium being cooled by theevaporators I2. l3 and I4, such as the temperature of the space being conditioned by the air conditioning unit. In this respect the valve 45 may be operated by an air motor 52 which receives air under pressure through pipe 53, adjustable orifice 54 and pipe 55 from a source of air under pressure 55. A bleed line 5! controlled by a controller 58 responsive to the temperature of the air in the space may be utilized for bleeding air from the air motor 52. When the space tem perature is high, say the controller 58 closes the bleed line 51 whereupon maximum air pressure is supplied to the air motor 52. Under these conditions the air motor 52 holds the valve 46 closed so that a maximum amount of liquid-refrigerant is being maintained within the evaporators I2, I3, and I4. As the space temperature decreases below 85 the controller 58 allows the bleed line 51 to decrease the pressure in the air motor 52 which allows the valve 46 to move towards the open position. As a result liquid refrigerant flows through the valve 45, the distributor 41 and pipes 48, 49 and 58 to the evaporators I2, I3 and I4 to decrease the amount of liquid refrigerant maintained in the evaporators I2, I3 and I4. Thus it is seen that the amount of liquid-refrigerant maintained in the evaporators I2, I3 and I4 may be varied in accordance with changes in space temperature. I

Since the refrigerant supplied to the evapor-' ators I2, I3 and I4 under the control of valve 45 is taken from the downstream side of the expansion valve 30, its effect in cooling the bulb 43 will be muchless than if itwere taken from the upstream side of the expansion valve 30. This permits the utilization of larger quantities of refrigerant for this purpose and, since the quantity is small in any event, makes it possible to control this refrigerant by a valve 45 which can be produced commercially in quantities. Also, the connection of the pipes 48, 49, and 50 to the evaporators I2, I3 and I4 at a point somewhat removed from their outlet ends and between their inlets and outlets permits this refrigerant to evaporate and become somewhat warmed up before it eflects the bulb 43. This again increases the quantity of refrigerant that may be utilized for the purpose of artificially cooling bulb 43 thereby rendering the quantity used sufliciently large to permit the valve 45-being of a type readily produced in quantities. This arrangement also insures that this added refrigerant will be evaporated and not in a liquid form when it reaches the sensitive element.

With the apparatus as thus far described, the

' distributor 41 should have a resistance less than that of the distributor I5. Atleast it should be no greater. When the valve 45 is wide open by reason of lowered room temperature, and since the resistance of distributor 41 is less than that of I 5, most of the refrigerant flow will go by way of distributor 41- and very little will go by way of distributor I5. In this manner, by properlyrelating the resistances of these distributors and by properly picking the points in evaporators I2, I3 and I4 at which the lines 48,. 49 and 50 are connected thereto, the manufacturer of the equipment can insure that no less than a predetermined minlmum quantity of refrigerant will be furnished to the evaporators.

If it be desired to control this minimum quantity of refrigerant even more accurately, the distributors I5 and 41 can be given the same resistance and the valve I! may be automatically controlled from the thermostatic controller 58.

line 53 by a pipe I5. Then when the space tem- III.

peratureis high and the bleed line closed off, the air pressure operating in motor l8 will hold valve vl'l open. As the space temperature decreases and the bleed 51 opens, the valve ll will gradually close as the valve opens and when the valve 46 is completely open then the valve II will be completely closed. .This will prevent all-flow of refrigerant to the inlets of evaporators l2, l3 and I4 b way of distributor l6 and the v sole supply of refrigerant to these evaporators will 'be by way of distributor ll By properly picking the size of distributor l1 and the points at which I desired amount of liquid refrigerant m the evaporators, conduit means for supplying liquid refrigerant frombetween the. expansion valve and the distributor to the evaporators for coolingethe thermostatic means-to change the amount of liquid refrigerant maintained in the evaporators and valve means in said conduit means for varying the flqw of liquid refrigerant through'the conduit-means to regulate the amount of liquid refrigerant maintained in the evaporators.

' 3.-A refrigeration system including a refrigpipes 48, 49 and 50 connect into the evaporators l2, l3 and I4, it will be possible to accurately determine the minimum capacity below which the evaporator will never be operated.

This same arrangement of course can be used where there is but a single evaporator in which case the distributors It and 41 would be eliminated and there would be but a single connection such as 48to the single evaporator.

If it be desired to control the amount of liquid refrigerant maintained in the-evaporators l2, l3

and I 4 in accordance with space relative humidity instead of space temperature, the controller would be made responsive to space relative" humidity. Under these conditions the controller erating apparatus having evaporator means in which refrigerant is evaporated and means for circulating refrig'erantthrough the evaporator means" comprising, the combination with said refrigerating apparatus of, a valve in control of the flow 'of refrigerant to the evaporator means,

a thermostatic device responsiveto the temperature of superheated refrigerant adjacent the outlet of the evaporator means for operating said valve to thereby regulate the flow of refrigerant I to the evaporator means, a conduit having one end connected between said valveand the evaporator means and its other end connected into 1 the evaporator means between the inlet and outlet thereof whereby refrigerant-may be supplied to a portion of said evaporator means to lower 58 responding to an increase in relative humidity would decrease the pressure in the air motor 52 to decrease the amount of liquid refrigerant main, tained in the evaporators l2, l3 and I4. As a result the temperature of theevaporators I 2, l3 and I 4 decreases to increase the amount of latent heat removal thereby.

Instead of utilizing the air operated control system described above it is 'obvious that an electric control system or a self-contained control system could be utilized and still remain within the scope of this invention, Although for purposes of illustration one form of this invention has been disclosed, other forms thereof may become apparent to those skilled in the art upon reference to this disclosure and therefore this invention is to be limited only by the scope of the appended claims.

I claim as my invention:

1. In combination with a refrigerating apparatus' having a plurality ofevaporators arranged in parallel for evaporating refrigerant, a

distributor for distributing liquid refrigerntto the evaporators, a common outlet for the evaporators and means for circulating refrigerant through the evaporators, a thermostatic expansion valve including thermostatic means responsive to the temperature of superheated refrigerant adjacent the common outlet for the evaporators the temperature of said portion of the evaporator ture of superheated refrigerant adjacent the outlet of the evaporator means for operating said valve to thereby regulate the flow of refrigerant to the evaporator means, a conduit having one end connected betweemsaid valve and the evaporator means and its othei' end connected into the evaporator means between the inlet and outlet thereof whereby refrigerant may be supplied to a portion of said evaporator means to lower the temperature of said portion of the evaporator means and thereby reduce the temperature to whichsaid thermostatic means iesponds, and valve means operable to simultaneously increase the flow of refrigerant through said conduit and for regulating the flow of liquid refrigerant to Y the evaporators through the distributor to maintain'a desired amount of liquid refrigerant in the evaporators, and means for supplying liquid refrigerant from between the expansion valve and the distributor to the evaporators for cooling the ;thermostatic means to change the amount of liquid refrigerant maintained in the evaporators.

2. In combination with arefrigerating apparatus havinga plurality of evaporators arranged in parallel for evaporating refrigerant, a distributor for distributing liquid refrigerant to the evaporators, acommon outlet for the evaporators and means for circulating refrigerant through the evaporators, a thermostatic expansion valve-including thermostatic means responsive to the temperature ofsuperheated refrigerant a acent thecommon outlet for the evaporators 4 .4 for: regulating the flow of liquid refrigerant to the evaporators through the distributor to maintaina ll means and thereby reduce the temperature to decrease the flow of refrigerant to the inlet of said evaporator means. ,5. A refrigeration system including a refrigerating apparatus having evaporator means in which refrigerant is evaporated and means for circulating refrigerant through the evaporator means comprising, the combination with said re-- frlgerating apparatus of, a valve in control of the flow of refrigerant to the evaporator means,

a thermostatic device responsive to the temperature of superheated refrigerant adjacent the out-- let of the evaporator means for operating said valve to thereby regulate the now of refrigerant to the evaporator means, a conduit having one end connec ed between said valve and the evaporator means. and its other end connected into the evaporator means between the inlet and outlet thereof whereby refrigerant may be supplied to a portion of said evaporator means to lower the temperature ofsaid-portion of the evaporator which said thermostatic means responds, and valve means operable to simultaneously stop the flow of refrigerant to the inlet of said evaporator means and increase the flow through said conduit to a maximum, whereby the minimum capacity at which the evaporator means can be operated is accurately determined.

6. A refrigeration system including a refrigerating apparatus having evaporator means in which refrigerant is evaporated and means for circulating refrigerant through the evaporator means for cooling a space, comprising, the combination with said refrigerating apparatus of a valve in control of the flow of refrigerant to the evaporator means, a thermostatic device responsive to the temperature of superheated refrigerant adjacent the outlet of the evaporator means for operating said valve to thereby regulate the flow of refrigerant to the evaporator means, a conduit having one end connected between said valve and the evaporator means and its other end connected into the evaporator means between the inlet and outlet thereof whereby refrigerant may be supplied to a portion of said evaporator means to lower the temperature of said portion of the evap- .which refrigerant is evaporated and means for circulating refrigerant through the evaporator means for cooling a space, comprising, the combination with said refrigerating apparatus of, a valve in control of the flow of refrigerant to the evaporator means, a thermostatic device responsive to the temperature of superheated refrigerant adjacent the outletof the evaporator means for operating said valve to thereby regulate the flow of refrigerant to the evaporator means, a conduit having one end connected between said valve and the evaporator means and its other end connected into the evaporator means between the inlet and outlet thereof whereby refrigerant may be supplied to a portion'of said evaporator means to lower the temperature of said portion of the evaporator means and thereby reduce the temperature to which said thermostatic means responds, and valve means controlled by space temperature for simultaneously decreasing the flow of refrigerant to the inlet of said evaporator means and increasing the fiow of refrigerant through said conduit.

8. In a refrigerating system, the combination of an evaporator having a plurality of conduits each having an inlet and an outlet, a refrigerant distributor connected to the inlet of each conduit, a single expansion valve for controlling flow of liquid refrigerant to the distributor, said single expansion valve including an element responsive to the temperature of the vaporizedrefrigerant discharged from the evaporator, means for withdrawing a restricted flow of liquid refrigerant from a portion of the refrigerating system containing liquid refrigerant at a pressure intermedi ate that of the supply. and the refrigerant pressure existing in the evaporator, said portion being between said valve and the inlets of said conduits', and supplying said withdrawn refrigerant to at least one of said conduits at a point remote from the inlet thereof, valve means whereby the flow through said withdrawing means ismodulatingly controlled, and means responsive to a condition brought about by evaporation of refrigerant in said evaporator controlling said last ALWIN B. NEWTON. 

